The corners on your screen are hot corners and give you access to different Windows features. Below, is a brief explanation of each of these corners.
Bottom Left-hand corner
The bottom left-hand hot corner of the screen will allow you to access the Start screen, if you're in the Start screen and have the Desktop open, this corner will open the Desktop from the Start screen.
Tip: Right-clicking in the left hand corner will open the power user menu.
Top-left corner of the screen
Moving the mouse to the top-left corner and then down will display all the apps running on the computer. Clicking and dragging any of these apps to the left or right-hand side of the screen will snap that app to that side of the screen. Each of these open app icons can also be right-clicked to close or snap.
Right-hand side of the screen
On the full right-hand side of the screen you will be given access to the Windows Charms.